Wash and scrub ginger well to remove any remaining bits of dirt or soil. Use a spoon to scrape off any thick or papery bits of skin. If using mature ginger, you will want to fully peel it.Thinly slice ginger across the grain using a vegetable peeler or mandoline (please watch your fingers)! You want the ginger to be as paper thin as possible, and I found the peeler to be the most effective way to do this.Place sliced ginger in a bowl. Pour 2 cups of boiling water over ginger and let sit for 5 minutes. If using mature ginger, you might want to blanch the ginger in a pot of boiling water for 5 to 10 minutes to soften it further.Drain well, then pack ginger into one pint jar or two half-pint (8 oz) mason jars. Be sure jars are thoroughly washed or, even better, sanitized in boiling water prior to using.In a saucepan, bring vinegar, sugar, and salt to a simmer, stirring until sugar is completely dissolved.Pour hot liquid over ginger in jars. Secure lids and allow the jars to cool to room temperature, then refrigerate. The pickled ginger, which is ready to eat after several hours, will keep in the refrigerator for up to six months.